Method of making a monoscope tube target



March 31, 1964 J. KABELL ETAL 3,126,610

METHOD OF MAKING A MONOSCOPE TUBE TARGET Filed May 6, 1960 41 (/M/NUM 100/5 4552; E4245 5. Jan/5s JNVENTORS United States Patent 3,126,610 METHQD OF MAKING A MONOSCOPE TUBE TARGET Louis J. Kabell and Earle D. Jones, Palo Alto, Calif, assignors to A. B. Dick Company Filed May 6, 1960, Ser. No. 27,334- 2 Claims. (Cl. 2925.17)

This invention relates to cathode-ray tubes employing secondary emission and, more particularly, to improvements therein.

The monoscope tube, manufactured, for example, by Radio Corporation of America and designated as the 21 21, is a well-known device usually used at television transmitters for the purposes of providing signals for testing and broadcasting test patterns. Effectively, these tubes produce an electrical signal which represents a static image which has been printed on the signal plate within the tube. The monoscope tube contains a flat plate of aluminum usually on the order of .004 inch thick, on which is printed with printers ink the image to be reproduced. In the process of heating the tube during its manufacture, the ink on the surface of the aluminum plate is reduced to pure carbon. This aluminum plate with the printing thereon is the target in the monoscope tube. As the scanning cathode-ray beam travels over the surface of the target, it causes more than twice as much electron emmision from the unprinted portions of the aluminum plate as from the portions covered over with carbon. The variations in secondary emission causes changes in the potential of a signal plate which is connected to the signal circuit.

It has been found that upon bombarding the aluminum surface in the monoscope tube with a cathode-ray beam, unless such surface has been very, very highly polished, it exhibits nonuniformities which cause spurious and unwanted signals to be developed in the course of scanning the target. The polishing of the aluminum surface to the degree necessary for eliminating these nonuniformities is a difficult and time-consuming operation.

An object of this invention is the provision of a monoscope target which, although not polished, does not cause spurious and unwanted signals to be developed.

Another object of the present invention is the provision of a new and improved monoscope target which has uniform characteristics.

Still another object of the present invention is the provision of a novel method and means for manufacturing an improved monoscope target which provides a high contrast.

These and other objects of the invention may be achieved by depositing a thin layer of metallic aluminum by evaporation in a vacuum on an insulating substrata, such as a glass plate. The evaporation process results in a very thin, uniform, and consistent layer of aluminum. The target is then cleaned and degreased. To provide areas of low secondary emission on the target, ordinary carboniferous printers ink is imprinted on the aluminized substrate by means of a rubber printing plate. The rubber plate is produced in a fashion similar to the methods used to make rubber stamps. After printing the target, it is baked in an inert atmosphere at a temperature such that the volatile materials of the ink are driven off, leaving practically pure carbon. The thin layer of aluminum, upon contact with the atmosphere, oxidizes and produces a high secondary-emitting surface.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in con nection with the accompanying drawings, in which:

FIGURE 1 is a plan view illustrative of a target in accordance with this invention; and

FIGURE 2 is a section through FIGURE 1.

Referring now to the drawings, in FIGURE 1 there is shown a plan view of the embodiment of the invention comprising a monoscope tube target 10, having letters 12 printed thereon by any suitable means. The target includes a substrate 14 of glass upon which there is a thin layer of metallic aluminum 16. The method of making this target comprises evaporating in a vacum a thin layer of metallic aluminum onto the substrate, here exemplified by a glass plate. The evaporation process results in a very thin, uniform, and consistent layer of aluminum.

The target is then cleaned and degreased. To provide areas of low secondary emission on the target, ordinary carboniferous printers ink is imprinted on the aluminum plate by means of a rubber printing plate. After printing, the target is baked in an inert atmosphere at a temperature such that the volatile materials of the ink are driven off, leaving practically pure carbon. The thin, uncovered layer of aluminum then, upon contact with the atmosphere, oxidizes and produces a very high secondary-emitting surface. The target may then be assembled in the monoscope tube in well-known fashion. No polishing of the aluminum surface is necessary.

There has been accordingly described and shown here a novel and useful method and means for obtaining a high quality monoscope target, wherein the aluminum surface is uniform and does not produce any spurious and unwanted signals. Further, a monoscope target made in accordance with the method and means descrbied herein provides a higher contrast between the printed and unprinted areas, thus improving the signal derived as the result.

We claim:

1. The method of making a monoscope tube target comprising evaporating a thin layer of metallic aluminum onto an insulating substrate, printing with ink a predetermined pattern on said aluminum layer, evapprating the volatile materials in said ink, and exposing said aluminum layer to the atmosphere to be oxidized.

2. The method of making a monoscope tube target comprising evaporating in a vacuum a thin layer of metal-lie aluminum onto a glass substrate, cleaning said aluminum layer, printing a predetermined pattern on said aluminum layer with carboniferous printing ink, baking said printed aluminum layer in an inert atmosphere until the volatile materials in said printing ink are evaporated and exposing said aluminum layer to the atmosphere to be oxidized.

References Cited in the file of this patent UNITED STATES PATENTS 2,229,556 Dumont et al. Jan. 21, 1941 2,287,415 Burnett June 23, 1942 2,392,879 Radcliffe Jan. 15, 1946 2,470,875 Snyder May 24, 1949 2,598,317 Teal May 27, 1952 2,790,228 Koda et al. Apr. 30, 1957 

1. THE METHOD OF MAKING A MONOSCOPE TUBE TARGET COMPRISING EVAPORATING A THIN LAYER OF METALLIC ALUMINUM ONTO AN INSULATING SUBSTRATE, PRINTING WITH INK A PREDETERMINED PATTERN ON SAID ALUMINUM LAYER, EVAPORATING THE VOLATILE MATERIALS IN SAID INK, AND EXPOSING SAID ALUMINUM LAYER TO THE ATMOSPHERE TO BE OXIDIZED. 